Antimicrobial Therapy of Chronic Sinusitis

Many of the pathogens found in chronically inflamed sinuses are resistant to penicillins through the production of beta-lactamase (8-11). These include both aerobic (S. aureus, H. influenzae, and M. catarrhalis) and anaerobic isolates (B. fragilis group and over half of the

TABLE 6 Empirical Antimicrobial Therapy in Acute Bacterial Sinusitis

Amoxicillin Therapy (high-dose) Mild illness

No history of recurrent acute sinusitis During summer months

When no recent antimicrobial therapy has been used

When patient has had no recent contact with patient(s) on antimicrobial therapy

When community experience shows high success rate of amoxicillin

Risk factors prompting a need for more effective antimicrobials3 Bacterial resistance is likely Antibiotic use in the past month, or close contact with a treated individual(s) Resistance common in community Failure of previous antimicrobial therapy Infection in spite of prophylactic treatment Child in daycare facility Winter season Smoker or smoker in family Presence of moderate-to-severe infection Presentation with protracted (more than 30 days) or moderate-to-severe symptoms Complicated ethmoidal sinusitis Frontal or sphenoidal sinusitis Patient history of recurrent acute sinusitis Presence of co-morbidity and extremes of life Co-morbidity (i.e., chronic cardiac, hepatic or renal disease, diabetes) Immunocompromised patient Younger than two years of age or older than 55 years Allergy to penicillin Allergy to penicillin or amoxicillin a Amoxicillin and clavulanic acid, 2nd and 3rd generation cephalosporins, and the "respiratory" quinolones.

Prevotella and Fusobacterium spp.). Retrospective studies illustrate the superiority of therapy effective against both aerobic and anaerobic BLPB in chronic sinusitis (26,75). Antimicrobials used for treatment of chronic sinusitis should be effective against both aerobic and anaerobic BLPB, as well as those resistant through other mechanisms. These agents include the combination of a penicillin (e.g., amoxicillin) and a beta-lactamase inhibitor (e.g., clavulanic acid), clindamycin, chloramphenicol, the combination of metronidazole and a macrolide, and the "newer" or "respiratory" quinolones (e.g., moxifloxacin). All of these agents (or similar ones) are available in oral and parenteral forms. Other effective antimicrobials are available only in parenteral form (e.g., cefoxitin, cefotetan, and carbapenems). Parenteral therapy with a

TABLE 7 Recommended Antibacterial Agents for Initial Treatment of Acute Sinusitis or After No Improvement

Factors prompting more

Clinical treatment failure at 48-72 hr

effective antibiotics3

At diagnosis

after starting treatment

No

High-dose amoxicillin

High-dose-amoxicillin/clavulanate or a "new" quinoloneb or cefuroxime or cefdinir or cefpodoxime proxetil

Yes

High-dose amoxicillin/clavulanate

High-dose amoxicillin/clavulanate

or a "new" quinoloneb

or a"new" quinoloneb

or cefuroxime-axetil

or cefuroxime-axetil

or cefdinir

or cefdinir

or cefpodoxime proxetil

or cefpodoxime proxetil

a See Table 7.

b Not approved for children (less than 18 yr).

a See Table 7.

b Not approved for children (less than 18 yr).

carbapenem (i.e., imipenem, meropenem, ertapenem) or tigecycline is more expensive, but provides coverage for most potential pathogens, both anaerobes and aerobes. If aerobic gramnegative organisms, such as P. aeruginosa, are involved, parenteral therapy with an aminoglycosides, a fourth-generation cephalosporin (cefepime or ceftazidime) or oral or parenteral treatment with a fluoroquinolone (only in postpubertal patients) is added. A beta lactam resistant penicillin is adequate for S. aureus. However, for methicillin resistant S. aureus, vancomycin, linezolid or tigecycline is needed. Therapy is given for at least 21 days, and may be extended up to 10 weeks. Fungal sinusitis can be treated with surgical debridement of the affected sinuses and antifungal therapy (76).

In contrast to acute sinusitis, which is generally treated vigorously with antibiotics, surgical drainage is the mainstay of the treatment of chronic sinusitis, especially in patients who had not responded to medical therapy. Impaired drainage may contribute to the development of chronic sinusitis, and correction of the obstruction helps to alleviate the infection and prevent recurrence. The use of antimicrobial therapy alone without surgical drainage of collected pus may not result in clearance of the infection. The chronically inflamed sinus membranes with diminished vascularity may not allow for an adequate antibiotic level to accumulate in the infected tissue, even when the blood level is therapeutic. Furthermore, the reduction in the pH and oxygen tension within the inflamed sinus can interfere with the antimicrobial activity, which can result in bacterial survival despite a high antibiotic concentration (5).

In the past, it was often necessary to resort to surgical intervention to cure chronic sinusitis. However, with improvements in the medical care, surgery is avoided more often. Functional endoscopic sinus surgery (FESS) has become the main surgical technique used; other surgical procedures serve only as a backup and are used especially when sinusitis is complicated by orbital and/or intracranial involvement. Although endoscopic surgery can provide up to 80% to 90% success in adults and children (77,78), a substantial number of patients suffer from complications (79) that warrant medical therapy being used to its full extent before resorting to surgery.

The surgeon's goals are to prevent persistence, recurrence, progression and complications of chronic sinusitis. This is achieved by complete removal of diseased tissue, preservation of normal tissue, production of drainage (or obliteration, if this is not possible) and consideration of the cosmetic outcome. Radical procedures should only be carried out if a simple approach, such as sinus lavage and medical therapy, fails or the disease is extensive.

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